Xsara HDI engine warm up...

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Jacko
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Xsara HDI engine warm up...

Post by Jacko » 24 Dec 2001, 17:22

Has anyone any experience with HDI's? I have a Xsara HDI 90 Estate which when started from cold takes about 10 miles before the engine reaches normal working temperature (just under 90 deg on the gauge). I suspect the thermostat is faulty, or is this normal for this type of engine?
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Dave Burns
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Post by Dave Burns » 24 Dec 2001, 18:58

On you next cold start, drive for 5 miles or when the gauge reaches the half way point, stop and feel the top hose, if the stat is opening early or stuck open the hose will be hot all the way to the rad, if the stat is ok the hose should still be cold at the rad end.
Direct injection diesels lose more heat to the exhaust than indirect injection engines because there is no combustion (swirl) chamber in the cylinder head, injection and combustion taking place directly in the cylinder hence Direct injection.
They wont heat up quite as fast but 10 miles to reach tepmerature sounds excessive.
MC and a HNY
Dave
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mbunting
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Post by mbunting » 26 Dec 2001, 17:29

The newer generation of direct injection diesels ( such as yours ), only inject as much fuel as is needed for the engine to give the performance you need. I used to have a Merc A-Class CDI diesel, this used to take loads of time to warm up on cool mornings, because it's not burning much fuel. In most modern direct injection diesels, there is an additional heater which runs on either diesel, or 1kw from the alternator, to boost the coolant temperature, therefore providing you with heat quicker !
I no longer have the Merc, I now have an old Xantia TD, which is warm within 1 - 2 miles, but only gives me 42mpg compared to the Mercs 54mpg ( and better speed ! )
So, basically, you've nothing to worry about. Don't bother leaving the car at idle to warm up, it won't work as it's bearly burning any fuel :-)
Regards
Mat
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Dave Burns
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Post by Dave Burns » 07 Jan 2002, 02:05

It would have been helpful if some other Peug/Cit. HDI owners had come along and said how far they had to drive for their car to reach normal operating temperature and the mpg they achieved, looks like there's no other taker's on the subject though so just a few words on what's been written above.
The amount of fuel going through the DI/HDI engine has nothing to do with how slowly they heat up compared to Indirect Injection engines, if you go over the figures you should reach that conclusion.
Regards
Dave
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mbunting
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Post by mbunting » 07 Jan 2002, 17:00

OK, Discussion time !
Let me say, I'm not professing to be an expert, but speak from experience of owning 2 IDI and 2 DI cars in the past, as well as my fathers experience with his Hdi.
Given your comments, would you expect a car with it's engine switched off to heat up as quickly as one on idle ?
The fuelling of a DI engine ( and hence combustion intensity ) is controlled by computer, it's job is to inject the least amount of fuel as possible to maintain the current demands on the engine by either the driver or other conditions.
The fuelling of an IDI car is controlled by a cable, directly controlled by the drivers foot. Fuelling is dependant on the position of the cable, and the atmospheric pressure alone, no other factors.
When there is little or no load on the engine, a computer controlled DI engine will reduce the fuelling dramatically, sometimes below the level to maintain idle ( momentum is carrying the car ).
Thats why the mpg display can go to 99mpg when going downhill with your foot off the accelerator, but may drop if you disengage the clutch - the momentum is lost and the computer compensates by burning more fuel.
In an IDI engine, the accelerator cable simply returns the fuelling lever back to idle, nothing more, nothing less.
In terms of heating up :
Merc A170Cdi : 15 mins @idle, 5-10 driving.
406 Hdi 110 : 10 mins @idle, 5-10 driving.
Xantia 1.9Td : 3 minutes @idle or driving.
In general driving, the following MPG have been achieved:
Merc : 60mpg.
406 : 52mpg.
Xantia : 42mpg.
Which do you think _burns_ less fuel, and therefore without assistance would take longer to warm up ?
Regards.
Mat.
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Dave Burns
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Post by Dave Burns » 08 Jan 2002, 07:41

Hello Mat, You haven't told me anything that I didn't already know having been around diesels for a long long time and from the very early age of 12 believe it or not, life in a farming comunity being a good bit different from town life, anyway to the nitty gritty.
I will dispence with the Merc. figures and compare like with like, my Xantia is at normal operating temperature at 2.6 miles and returns a similar mileage per gallon as yours.

Xantia td @ 42mpg burns approx 108ml of fuel per mile and is at norm. temp at 2.6 miles having consumed 281ml of fuel.
406 HDI @ 52mpg burns approx 87.5ml of fuel per mile and is at norm temp at 5 miles having consumed 437ml of fuel.
So you see Mat, despite the 406 HDI being some 24% more fuel efficient, it actualy has to burn 55.5% more fuel than the Indirect Injection Engine to reach the same temperature.
That in a nut shell using your own figures is your argument destroyed. The grater fuel efficiency of DI/HDI was never in dispute, just the heat up time of the two engine designs and the reasons for it.
So why does the Indirect Injection Engine compared to the HDI Engine get hot in only half the distance and on 55.5% less fuel, as I said in my first post on this subject it was because the Direct Injection Engine lost more heat to the exhaust than IDI because it does not have a Combustion (swirl) Chamber in the cylinder head, the swirl chamber (also known as the Hot spot, and for good reason) in the IDI engine has a throat or passage connecting it to the cylinder, this passage enters the combustion chamber in the cylinder head tangientaly, compressed air is forced into the combustion chamber by the piston at very high speed and because of it's design causes the air to swirl vigoursely within it mixing it with the fuel being injected, on contact with the hot air the fuel vaporises instantly, shortly after autoignition of the fuel then occurs, the hot burning and swirling gas imparts massive amounts of heat to the walls of the combustion chamber (due to a process exactly oposit to that of wind chill, a hot moving gas will heat a surface much faster than a hot still gas, just as cold moving air will rob heat from a surface much faster than cold still air) and the throat or passage (hot spot) as it jets out into the cylinder where it does what we want it to by driving the piston down the cylinder turning the crankshaft, the fact that the gas has to travel down this passage and can't all jump into the cylinder at once plus the heat loss to the cylinder head are where the main deficiencies lie in the Indirect Injection Engine compared to the DI or HDI, if you take a hot compressed (simple element) gas and cool it by any degree you will lower it's pressure to some extent.
The direct injection engine on the other hand, does not give up the heat from combustion so readily to the cylinder wall or cylinder head which results in part of it's better efficiency, plus all of the expanding gas is at once able to exert pressure on the piston since combustion is taking place directly in the cylinder, gas is not throttled by travelling down any passage from any other chambers, another big plus for DI over IDI
The link's below don't go into anything like this amount of detail but there are a few choice words from these credible sources on the subject that should nail it for you should you still not be persuaded.
http://www.memagazine.org/backissues/au ... iesel.html
http://www.mitsubishi-motors.co.jp/inter/NEWS/9926.html
Regards Dave
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Micky
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Post by Micky » 12 Jan 2002, 04:36

110 HDi Xantia, no warm air for 3 miles and 50 mpg. 2.8V6 Granada hot air after 200 yds but 23 mpg. Why? HDi efficient convertor of fuel to forwards motion (1990's engine design), Ford V6 inefficient convertor of fuel to forwards motion (1970's engine design).....great heater though!
Micky
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neilminto
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Post by neilminto » 14 Jan 2002, 02:50

Interesting stuff - enjoyed the debate Dave. Just for comparison, my Xantia Estate (110 HDi) is fully warm in about 5 miles but consistently - brim to brim every tankful - gets 44 to 45 mpg on BP or Shell low-sulphur diesel. My ZX TD estate used to get 41-42, but in fairness to the Xantia I probably drive it harder.
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alf
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Post by alf » 28 Jan 2002, 06:02

If its quicker heat in the cabin that you require, I remember seeing a 'readers offer' type advert in the press where they were flogging a small car heater which runs from the fag lighter 180 watts if I remember.
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